When signals based on a code division multiple access (CDMA) method are demodulated, chip equalizers may sometimes be used. In a chip equalizer, the weight of the equalizer is determined such that the average error power becomes the minimum with respect to multiplexed reception signals that have not been subjected to de-spreading. However, in a reception method, such as High-Speed Downlink Packet Access (HSDPA) or the like, that uses CDMA and Multiple-Input and Multiple-Output (MIMO) in combination, it is known that the receiving performance of BER or the like is further improved if the weight of the equalizer is determined such that the average error power becomes the minimum with respect to the reception signals that have been subjected to de-spreading, rather than with respect to reception signals that have not been subjected to de-spreading.
Patent Document 1: Japanese National Publication of International Patent Application No. 2013-505610
Non-Patent Document 1: Byoung-Hoon Kim, Xiaoxia Zhang, Flury, M., “Linear MMSE space-time equalizer for MIMO multicode CDMA systems”, IEEE Trans. Communications, Vol. 54, No. 10, pp. 1710-1714, Oct. 2006.
When calculating the weight of an equalizer in which the average error power is the minimum with respect to the reception signals that have been subjected to de-spreading, for example, the spreading factor is used as one of the parameters. Accordingly, if the spreading factor differs, the weight of the equalizer also differs. Consequently, as in the HSDPA method, in the reception method that uses CDMA and MIMO in combination, instead of equalizers that are conventionally used, equalizers in which the weight of the equalizers can be changed in accordance with the spreading factor are provided. This increases the cost of the receiving devices.